1. Field of the Invention
The present invention concerns a method for determining the magnetization transfer constant for spin echo magnetic resonance imaging sequences, and a magnetic resonance imaging apparatus that implements such a method.
2. Description of the Prior Art
The magnetization transfer is based on the fact that an interaction takes place between the water protons and other protons that are bonded in macromolecules. Upon the excitation of the protons in the macromolecules by an RF pulse, the saturation of these other protons is transferred to the water protons. In MR imaging, this transference of the magnetization can be observed as a weakened signal from the water protons, the weakening being dependant on the magnetization transfer. The calculation of a magnetization transfer coefficient is important in several clinical problems with regard to brain imaging, mammography, and in examinations of cartilage, as examples. Typically, the magnetization transfer coefficient (MTC) is calculated from data acquisitions done with a special magnetization transfer saturation pulse, which is emitted at a frequency outside of that of the water proton resonance, in order to saturate the longitudinal magnetization of the protons in the macromolecules (see Henkelmann R. M. et al, “Magnetisation Transfer in MRI: A review”, NWR Biomedicine 14, 57-64). This type of calculation requires a lengthy scanning period, which affects usage of the apparatus during the clinical routine.